I want to add a new column to all tables with table name pattern table_<>_details.
I use this query :
select 'alter table ' || table_name || ' ADD COLUMN CREATED TIMESTAMP;'
from information_schema.tables
where table_name like 'table_%_details';
to generate the DDL queries which looks like :
alter table table_1_details ADD COLUMN CREATED TIMESTAMP;
alter table table_2_details ADD COLUMN CREATED TIMESTAMP;
alter table table_3_details ADD COLUMN CREATED TIMESTAMP;
alter table table_4_details ADD COLUMN CREATED TIMESTAMP;
alter table table_5_details ADD COLUMN CREATED TIMESTAMP;
alter table table_6_details ADD COLUMN CREATED TIMESTAMP;
alter table table_7_details ADD COLUMN CREATED TIMESTAMP;
I tried to loop through these records using the following script :
do $$ declare c_query cursor for
select
'alter table ' || table_name || ' ADD COLUMN CREATED TIMESTAMP;'
from
information_schema.tables
where
table_name like 'table_%_details';
begin
for rec in c_query loop
execute rec;
end loop;
close c_query;
end $$
I have tried to fine tune this script but with no success, I'm getting the following error:
SQL Error [42601]: ERROR: syntax error at or near ""alter table table_1_details ADD COLUMN CREATED TIMESTAMP;""
Where: PL/pgSQL function inline_code_block line 13 at EXECUTE statement
my question is how to modify this scrip to loop through all these results and apply the DDL to database , note (I do not want to create functions).
please any Ideas will be appreciated.
Just loop over the resultset of infomation_schema.tables and then use EXECUTE with your concatenated ALTER TABLE statements
DO $$
DECLARE
row record;
BEGIN
FOR row IN SELECT table_name FROM information_schema.tables
WHERE table_name LIKE 'table_%_details' LOOP
EXECUTE 'ALTER TABLE ' || row.table_name || ' ADD COLUMN CREATED TIMESTAMP;';
END LOOP;
END;
$$;
EDIT: Alternatively you can use FORMAT to concatenate your strings instead of using ||, as pointed out by #a_horse_with_no_name
EXECUTE FORMAT('ALTER TABLE %I ADD COLUMN CREATED TIMESTAMP;',row.table_name);
Check this db<>fiddle
I am new to postgres. I need to create a function that will take a list of all the tables in the database whose names are stored in one table and then delete the records of all the tables that are older than x days and have a certain row_status. Some tables do not have a row_status column.
I get an error when I try to save a written function in dbeaver -> ERROR: syntax error at or near "||"
create function delete_old_records1(day1 int, row_status1 character default null, row_status2 character default null)
returns void
language plpgsql
as $$
declare
c all_tables1%rowtype;
begin
for c in select * from all_tables1 loop
if exists(SELECT column_name FROM information_schema.columns
WHERE table_schema = 'yard_kondor' AND table_name =c.table_name AND column_name = 'row_status') then
execute 'delete from '||c.table_name||' where row_create_datetime>current_date-day1+1 and
row_status in (coalesce(row_status1,''P''), row_status2)';
else
execute 'delete from '||c.table_name||' where row_create_datetime>current_date-day1+1';
raise notice 'Table '||c.table_name||' does not have row_status column';
end if;
end loop;
return;
commit;
end;
$$
Your immediate problem is this line:
raise notice 'Table '||c.table_name||' does not have row_status column';
That should be:
raise notice 'Table % does not have row_status column', c.table_name;
However, your function could be improved a bit. In general it is highly recommended to use format() to generate dynamic SQL to properly deal with identifiers. You also can't commit in a function. If you really need that, use a procedure.
create function delete_old_records1(day1 int, row_status1 character default null, row_status2 character default null)
returns void
language plpgsql
as $$
declare
c all_tables1%rowtype;
begin
for c in select * from all_tables1
loop
if exists (SELECT column_name FROM information_schema.columns
WHERE table_schema = 'yard_kondor'
AND table_name = c.table_name
AND column_name = 'row_status') then
execute format('delete from %I
where row_create_datetime > current_date - %J + 1
and row_status in (coalesce(row_status1,%L), row_status2)', c.table_name, day1, 'P');
else
execute format('delete from %I where row_create_datetime > current_date - day1 + 1', c.table_name);
raise notice 'Table % does not have row_status column', c.table_name;
end if;
end loop;
return;
-- you can't commit in a function
end;
$$
Thank you for answer. Now I'm able to save function, but currently I have a problem with running the function.
I started the function with:
DO $$ BEGIN
PERFORM "delete_old_records1"(31,'P','N');
END $$;
I started script with ALT+X (also tried select delete_old_records1(31,'P','N');) and have this error:
SQL Error [42703]: ERROR: column "day1" does not exist
Where: PL/pgSQL function delete_old_records1(integer,character,character) line 11 at EXECUTE statement
SQL statement "SELECT "delete_old_records1"(31,'P','N')"
PL/pgSQL function inline_code_block line 2 at PERFORM
I am trying to list all contrains that fulfills an criteria and then drop them,
DO $$
DECLARE r RECORD;
BEGIN
FOR r in SELECT
conrelid::regclass,
conname
FROM
pg_constraint
WHERE
contype IN ('u')
AND connamespace = 'public'::regnamespace
AND conname ~* '_key'
LOOP
EXECUTE 'ALTER TABLE % DROP CONSTRAINT %',r.conrelid, r.conname;
END LOOP;
END;
$$
When I execute this I get
ERROR: query "SELECT 'ALTER TABLE % DROP CONSTRAINT %',r.conrelid, r.conname" returned 3 columns
CONTEXT: PL/pgSQL function inline_code_block line 14 at EXECUTE
SQL state: 42601
Why is 3 columns returned?
You can't pass identifiers like that to a dynamic SQL. Use format() instead:
EXECUTE format('ALTER TABLE %I DROP CONSTRAINT %I', r.conrelid::text, r.conname::text);
The function is created fine, but when I try to execute it, I get this error:
ERROR: relation "column1" does not exist
SQL state: 42P01
Context: SQL statement "ALTER TABLE COLUMN1 ADD COLUMN locationZM geography (POINTZM, 4326)"
PL/pgSQL function addlocationzm() line 6 at SQL statement
Code:
CREATE OR REPLACE FUNCTION addlocationZM()
RETURNS void AS
$$
DECLARE
COLUMN1 RECORD;
BEGIN
FOR COLUMN1 IN SELECT f_table_name FROM *schema*.geography_columns WHERE type LIKE 'Point%' LOOP
ALTER TABLE COLUMN1 ADD COLUMN locationZM geography (POINTZM, 4326);
END LOOP;
END;
$$
LANGUAGE 'plpgsql';
SELECT addlocationZM()
I'm probably just being dumb, but I've been at this for a while now and I just can't get it. The SELECT f_table_name ... statement executed on its own returns 58 rows of a single column, each of which is the name of a table in my schema. The idea of this is to create a new column, type PointZM, in each table pulled by the SELECT.
The function would work like this:
CREATE OR REPLACE FUNCTION addlocationZM()
RETURNS void AS
$func$
DECLARE
_tbl text;
BEGIN
FOR _tbl IN
SELECT f_table_name FROM myschema.geography_columns WHERE type LIKE 'Point%'
LOOP
EXECUTE
format('ALTER TABLE %I ADD COLUMN location_zm geography(POINTZM, 4326)', _tbl);
END LOOP;
END
$func$ LANGUAGE plpgsql;
Note how I use a simple text variable to simplify matters. You don't need the record to begin with.
If it's a one-time operation, use a DO command instead of creating a function:
DO
$do$
BEGIN
EXECUTE (
SELECT string_agg(
format(
'ALTER TABLE %I ADD COLUMN location_zm geography(POINTZM, 4326);'
, f_table_name)
, E'\n')
FROM myschema.geography_columns
WHERE type LIKE 'Point%'
);
END
$do$;
This is concatenating a single string comprised of all commands (separated with ;) for a single EXECUTE.
Or, especially while you are not familiar with plpgsql and dynamic SQL, just generate the commands, copy/paste the result and execute as 2nd step:
SELECT 'ALTER TABLE '
|| quote_ident(f_table_name)
|| ' ADD COLUMN locationZM geography(POINTZM, 4326);'
FROM myschema.geography_columns
WHERE type LIKE 'Point%';
(Demonstrating quote_ident() this time.)
Related:
Table name as a PostgreSQL function parameter
Aside: Unquoted CaMeL-case identifiers like locationZM or your function name addlocationZM may not be such a good idea:
Are PostgreSQL column names case-sensitive?
Question is simple. How to add column x to table y, but only when x column doesn't exist ? I found only solution here how to check if column exists.
SELECT column_name
FROM information_schema.columns
WHERE table_name='x' and column_name='y';
With Postgres 9.6 this can be done using the option if not exists
ALTER TABLE table_name ADD COLUMN IF NOT EXISTS column_name INTEGER;
Here's a short-and-sweet version using the "DO" statement:
DO $$
BEGIN
BEGIN
ALTER TABLE <table_name> ADD COLUMN <column_name> <column_type>;
EXCEPTION
WHEN duplicate_column THEN RAISE NOTICE 'column <column_name> already exists in <table_name>.';
END;
END;
$$
You can't pass these as parameters, you'll need to do variable substitution in the string on the client side, but this is a self contained query that only emits a message if the column already exists, adds if it doesn't and will continue to fail on other errors (like an invalid data type).
I don't recommend doing ANY of these methods if these are random strings coming from external sources. No matter what method you use (client-side or server-side dynamic strings executed as queries), it would be a recipe for disaster as it opens you to SQL injection attacks.
Postgres 9.6 added ALTER TABLE tbl ADD COLUMN IF NOT EXISTS column_name.
So this is mostly outdated now. You might use it in older versions, or a variation to check for more than just the column name.
CREATE OR REPLACE function f_add_col(_tbl regclass, _col text, _type regtype)
RETURNS bool
LANGUAGE plpgsql AS
$func$
BEGIN
IF EXISTS (SELECT FROM pg_attribute
WHERE attrelid = _tbl
AND attname = _col
AND NOT attisdropped) THEN
RETURN false;
ELSE
EXECUTE format('ALTER TABLE %s ADD COLUMN %I %s', _tbl, _col, _type);
RETURN true;
END IF;
END
$func$;
Call:
SELECT f_add_col('public.kat', 'pfad1', 'int');
Returns true on success, else false (column already exists).
Raises an exception for invalid table or type name.
Why another version?
This could be done with a DO statement, but DO statements cannot return anything. And if it's for repeated use, I would create a function.
I use the object identifier types regclass and regtype for _tbl and _type which a) prevents SQL injection and b) checks validity of both immediately (cheapest possible way). The column name _col has still to be sanitized for EXECUTE with quote_ident(). See:
Table name as a PostgreSQL function parameter
format() requires Postgres 9.1+. For older versions concatenate manually:
EXECUTE 'ALTER TABLE ' || _tbl || ' ADD COLUMN ' || quote_ident(_col) || ' ' || _type;
You can schema-qualify your table name, but you don't have to.
You can double-quote the identifiers in the function call to preserve camel-case and reserved words (but you shouldn't use any of this anyway).
I query pg_catalog instead of the information_schema. Detailed explanation:
How to check if a table exists in a given schema
Blocks containing an EXCEPTION clause are substantially slower.
This is simpler and faster. The manual:
Tip
A block containing an EXCEPTION clause is significantly more
expensive to enter and exit than a block without one.
Therefore, don't use EXCEPTION without need.
Following select query will return true/false, using EXISTS() function.
EXISTS(): The argument of EXISTS is an arbitrary SELECT statement, or
subquery. The subquery is evaluated to determine whether it returns
any rows. If it returns at least one row, the result of EXISTS is
"true"; if the subquery returns no rows, the result of EXISTS is
"false"
SELECT EXISTS(SELECT column_name
FROM information_schema.columns
WHERE table_schema = 'public'
AND table_name = 'x'
AND column_name = 'y');
and use the following dynamic SQL statement to alter your table
DO
$$
BEGIN
IF NOT EXISTS (SELECT column_name
FROM information_schema.columns
WHERE table_schema = 'public'
AND table_name = 'x'
AND column_name = 'y') THEN
ALTER TABLE x ADD COLUMN y int DEFAULT NULL;
ELSE
RAISE NOTICE 'Already exists';
END IF;
END
$$
For those who use Postgre 9.5+(I believe most of you do), there is a quite simple and clean solution
ALTER TABLE if exists <tablename> add if not exists <columnname> <columntype>
the below function will check the column if exist return appropriate message else it will add the column to the table.
create or replace function addcol(schemaname varchar, tablename varchar, colname varchar, coltype varchar)
returns varchar
language 'plpgsql'
as
$$
declare
col_name varchar ;
begin
execute 'select column_name from information_schema.columns where table_schema = ' ||
quote_literal(schemaname)||' and table_name='|| quote_literal(tablename) || ' and column_name= '|| quote_literal(colname)
into col_name ;
raise info ' the val : % ', col_name;
if(col_name is null ) then
col_name := colname;
execute 'alter table ' ||schemaname|| '.'|| tablename || ' add column '|| colname || ' ' || coltype;
else
col_name := colname ||' Already exist';
end if;
return col_name;
end;
$$
This is basically the solution from sola, but just cleaned up a bit. It's different enough that I didn't just want to "improve" his solution (plus, I sort of think that's rude).
Main difference is that it uses the EXECUTE format. Which I think is a bit cleaner, but I believe means that you must be on PostgresSQL 9.1 or newer.
This has been tested on 9.1 and works. Note: It will raise an error if the schema/table_name/or data_type are invalid. That could "fixed", but might be the correct behavior in many cases.
CREATE OR REPLACE FUNCTION add_column(schema_name TEXT, table_name TEXT,
column_name TEXT, data_type TEXT)
RETURNS BOOLEAN
AS
$BODY$
DECLARE
_tmp text;
BEGIN
EXECUTE format('SELECT COLUMN_NAME FROM information_schema.columns WHERE
table_schema=%L
AND table_name=%L
AND column_name=%L', schema_name, table_name, column_name)
INTO _tmp;
IF _tmp IS NOT NULL THEN
RAISE NOTICE 'Column % already exists in %.%', column_name, schema_name, table_name;
RETURN FALSE;
END IF;
EXECUTE format('ALTER TABLE %I.%I ADD COLUMN %I %s;', schema_name, table_name, column_name, data_type);
RAISE NOTICE 'Column % added to %.%', column_name, schema_name, table_name;
RETURN TRUE;
END;
$BODY$
LANGUAGE 'plpgsql';
usage:
select add_column('public', 'foo', 'bar', 'varchar(30)');
Can be added to migration scripts invoke function and drop when done.
create or replace function patch_column() returns void as
$$
begin
if exists (
select * from information_schema.columns
where table_name='my_table'
and column_name='missing_col'
)
then
raise notice 'missing_col already exists';
else
alter table my_table
add column missing_col varchar;
end if;
end;
$$ language plpgsql;
select patch_column();
drop function if exists patch_column();
In my case, for how it was created reason it is a bit difficult for our migration scripts to cut across different schemas.
To work around this we used an exception that just caught and ignored the error. This also had the nice side effect of being a lot easier to look at.
However, be wary that the other solutions have their own advantages that probably outweigh this solution:
DO $$
BEGIN
BEGIN
ALTER TABLE IF EXISTS bobby_tables RENAME COLUMN "dckx" TO "xkcd";
EXCEPTION
WHEN undefined_column THEN RAISE NOTICE 'Column was already renamed';
END;
END $$;
You can do it by following way.
ALTER TABLE tableName drop column if exists columnName;
ALTER TABLE tableName ADD COLUMN columnName character varying(8);
So it will drop the column if it is already exists. And then add the column to particular table.
Simply check if the query returned a column_name.
If not, execute something like this:
ALTER TABLE x ADD COLUMN y int;
Where you put something useful for 'x' and 'y' and of course a suitable datatype where I used int.